Hey Ken,

So sorry, by the way, what is this pointer used for? I dun quite understand?
Can advise me?

I2C_Address &= 0x58;

Is this the right way of writing it?

void MAX517( unsigned char data_DAC, unsigned char I2C_Address )
 {
 I2C_Address &= 0x58;   // Source address byte to WRITE mode

 StartI2C();            // Start condition

 WriteI2C(I2C_Address); // Address byte of DAC

 WriteI2C(0x00);        // Command byte

 WriteI2C(data_DAC);    // Output Data

 StopI2C();             // Stop condition
 }

Nicholas

----- Original Message -----
From: "Ken Pergola" <no_spam@LOCALNET.COM>
To: <PICLIST@MITVMA.MIT.EDU>
Sent: Friday, March 19, 2004 12:21 AM
Subject: Re: [PIC]:I2C DAC test


> Hi Nicholas,
>
> Nicholas you definitely want to initialize 'I2C_Address' otherwise your
code
> will not work:
>
> Try this:
>
>      char I2C_Address = 0x58;
>
> Instead of:
>      char I2C_Address;
>
>
>
> The actual 7-bit slave device address for the way you wired the MAX517
(with
> pins AD1, AD0 grounded) is 0x2C.
> But when the slave address is coerced into the 8-bit 'I2C_Address' because
> of the R/W bit, it becomes 0x58.
> So you did your homework well and came up with 0x58. :)
>
> Nicholas, I think your best course of action is to test the function
return
> code of the 'WriteI2C()' function like I mentioned in my last post. This
> will provide you with some useful information. You should really test and
> act upon the function return code in future code, but for now, just test
the
> return value to see what you get.
>
> I've always written my own I2C routines in HI-TECH PICC, PICC-18, and
> PICC-Lite. I have never used the Microchip C18 compiler.
> You main goal is to see if your slave ACKs your control byte correctly --
I
> would imagine that this status is reflected in 'WriteI2C()' funtion code
> status.
>
> Nicholas, in your pinout you said 'Pin 8 - No connection' -- this is where
> you want to feed your voltage reference.
> Isn't this the pin you said yesterday you connected to a voltage divider?
> I'm confused now. You definitely do not want that pin as a NO CONNECT
since
> that's you voltage reference input. You could tie that pin to Vdd for now.
> Then if you sent 0x7F to the DAC (output byte) you would expect
> approximately Vdd/2 on your DAC output pin.
>
> I'm about a day away from a Master I2C/SMBus Engine (MISE) release that
> could validate your project I2C hardware in a few minutes.
> The MISE utility give you interactive feedback on your I2C transactions so
> that you'll know if the START condition worked, if the control byte was
> ACKed by the slave, etc.
>
>
> I'm assuming that the MAX517 does not have a half-buffered output (some
DACs
> like the TLC5620 do) -- just check the data sheet to make sure.
>
>
> Make that change I mentioned above and please report back.
>
> Good luck.
>
> Ken Pergola
>
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